The present invention relates generally to methods and apparatuses for making tissue products. More particularly, the invention relates to methods and apparatuses for drying wet webs with can dryers in a manner that maintains web bulk.
Bulk is an important property of tissue products such as facial and bath tissue, napkins and paper towels. The bulk of a tissue contributes to the actual and perceived softness and absorbency of the tissue.
While a great deal of effort has been directed toward machine configurations and processes for building bulk into a wet web, a significant portion of that bulk is subsequently removed from the wet web when it is dried to its final dryness. This appears to be particularly the case with can dryers. In a conventional can drying apparatus, the wet web is held between a dryer felt or dryer fabric and the surface of each can dryer.
The effect of such a conventional can drying apparatus can be to significantly decrease the bulk of the web. The repeated pressing, releasing and pressing of the wet web against the can dryers can function to iron the web. In a conventional afterdryer section utilizing can dryers, for example, it is believed that the bulk of a wet web can be decreased by as much as one-third or more from the creping blade to the reel. As a consequence, the actual and perceived softness and absorbency of the web is reduced.
Therefore, what is lacking and needed in the art is an improved can drying process that does not iron a significant amount of bulk out of the wet web when it is being dried. A related can drying apparatus to achieve this result is also needed.